Abstract
Orange juice has become one of the most widely accepted natural beverages due to its invigorating flavours, source of quick energy in the form of natural sugars and its nutrient which support the growth of acid tolerant bacteria, yeasts and moulds. Present investigation was conducted to study the microbiological examination of commercially and freshly prepared orange juices. Freshly prepared orange juices were pasteurised, carbonated, concentrated and chemically treated with a preservative (sodium metabisulphite) and stored under, freezer, refrigeration and ambient temperature for 90 days. The pH ranged from 3.0 to 4.5 for the commercially, fresh and stored samples respectively. The total bacterial load ranged from 1.6x105 to 3.6x106 and the total yeast cell counts ranged from 1.7x104 to 4.8x106 cfu/ml for the commercially, freshly and stored samples. Twenty-two microbial species including 5 bacterial isolates, 6 yeast isolates and 11 isolates of mould were isolated from the orange juices. The bacterial isolates identified from the samples were Bacillus megaterium, Bacillus cereus, Bacillus pantothenticus, Bacillus aeruginosa and Escherichia coli. The fungal isolates were Saccharomyces cerevisiae, Saccharomyces rouxii, Saccharomyces telluris, Blastomyces sp, Aspergillus sp, Mycelia sp, Chrysosporium sp, and Trichoderma sp. Among the bacterial isolates, Bacillus sp was the predominant, while the fungi Saccharomyces sp and Mycelia sp were the predominant fungi and accounted for five out of 11 isolates. The isolates of bacteria, yeasts and moulds appear to be persistent throughout the period of this study and could be used as indicators of microbial quality. A safe microbial load and reduction in contamination of orange juice /fruit juices can be achieved by combination of processing methods such as chemical preservatives with pasteurisation,concentration with carbonation under controlled microbiological environments such as freezer and refrigeration temperatures.
Highlights
Consumption of fresh juices increased drastically due to its freshness, high vitamin content and low calories [1]
It shows that the total aerobic plate counts (TAPC) per ml for all the samples for bacteria ranged from 1.50x105 to 4.1x106cfu/ml
The refrigerated samples had the counts of 1.7x104, 1.7x104 and 4.75x106cfu/ml for concentrated, carbonated, chemically treated and pasteurised respectively, while the counts for the samples stored under ambient temperatures had counts of 8.0x105, 9.2x104, 2.5x106 and 3.4x106cfu/ml for carbonated, chemically treated, pasteurised and concentrated respectively
Summary
Consumption of fresh juices increased drastically due to its freshness, high vitamin content and low calories [1]. It is prepared by mechanically squeezing or macerating without the application of heat or solvent [2] and may in the home from fresh fruits and vegetables using variety of hand and electric juicers [3]. It is estimated that about 20-25% of the harvested fruits are destroyed by pathogens during post-harvest handling even in developed countries [4,5,6]. Post-harvest losses are often more severe due to inadequate storage and transportation facilities [4]. Pathogenic organisms can enter fruits and vegetables through damaged surfaces, such as punctures, wounds, cuts and splits that occur during growing or harvesting [7]
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